Field of the Invention
Embodiments of the invention generally relate to apparatus and methods for removing material from a wellbore. Particularly, embodiments of the invention relate to a magnetic retrieval apparatus. Embodiments of the invention also relate to apparatus and methods of assembling a magnetic retrieval apparatus.
Description of the Related Art
Many operations in an oil or gas well often produce a variety of debris in the wellbore. For example, milling operations may produce metallic mill cuttings, which may not be completely removed by circulation of fluid in the wellbore. Also, bit cones, slips, tong pins, and hammers, or fragments thereof, can collect at the bottom of the wellbore.
Retrieval tools containing magnets have been used to retrieve the debris in the wellbore. One type of retrieval tool includes a plurality of magnets disposed on its exterior, and the magnets may be exposed to the wellbore environment surrounding the retrieval tool. The exposed magnets are subjected to physical damage or corrosion in the wellbore, and in some instances, may even be lost in the wellbore.
The handling of magnets during assembly of the retrieval tool raises safety concerns. Large, high strength magnets may be pulled out of the operator's hand by an adjacent magnet.
There is a need, therefore, for an improved retrieval tool for retrieving debris from the wellbore. There is also a need for apparatus and methods of assembling a retrieval tool.